A group of students in the US have developed nail polish that detects date-rape drugs in drinks(Flickr)

Four students in the US have invented a novel way of protecting women from sexual assault on nights out - a nail polish that detects the presence of date-rape drugs.

A group of undergraduates in the Materials Science & Engineering department at North Carolina State University are developing a nail varnish called Undercover Colors that reacts when it comes into contact with drugs such as Rohypnol, GHB and Xanax.

Stephen Gray, Ankesh Madan, Tasso Von Windheim and Tyler Confrey-Maloney conceived the idea after forming a team on the university's Engineering Entrepreneurs Program.

"While date-rape drugs are often used to facilitate sexual assault, very little science exists for their detection. Our goal is to invent technologies that empower women to protect themselves from this heinous and quietly pervasive crime," the students' Facebook page reads.

"With our nail polish, any woman will be empowered to discreetly ensure her safety by simply stirring her drink with her finger. If her nail polish changes colour, she'll know that something is wrong."

The team was granted $11,250 (£6,600) from North Carolina State's Entrepreneurship Initiative, which aims to develop solutions to "real-world challenges". Each of the students personally know someone who has been sexually assaulted.

Madan told Higher Education Works: "As we were thinking about big problems in our society, the topic of drug-facilitated sexual assault came up. All of us have been close to someone who has been through the terrible experience and we began to focus on finding a way to help prevent the crime.

"We wanted to focus on preventive solutions, especially those that could be integrated into products that women already use. And so the idea of creating a nail polish that detects date rape drugs was born."

Undercover Colors won the Lulu eGames in April and recently reached the semi-final of the K50 start-up showcase. The students are still in the process of researching and developing their product with the help of donations.

A White House task force report released this year showed one in five American female students reported being attacked.

Yet the development of the nail polish has been criticised by some for placing a sticking plaster over the problem, rather than addressing the root of the issue.

"The problem isn't that women don't know when there are roofies in their drink; the problem is people putting roofies in their drink in the first place," Rebecca Nagle, a co-director of the activist group Force: Upsetting Rape Culture, told ThinkProgress.org.